Conventional moving walkways for the indicated purpose are formed by a band of pallets which move on side guides, which pallets are secured and fitted on a structure supporting the weight of the components and users. The walkways are further provided with a glass or opaque balustrade which is also secured to the same support structure and on which a handrail moves at the same speed as the pallets.
Conventional systems for transporting passengers/goods such as moving walkways include a chain of conveyor pallets which move in a track for the purpose of providing a continuous movement along a specific path. The conveyor pallets are connected to said chain track which moves as a result of a drive system. The drive system normally consists of a chain of conveyor plates, cogged wheels, a shaft and an electric geared motor. The electric motor drives the shaft to which there are integrally attached cogged wheels, which transmit the movement to the links of the chain of conveyor pallets. The conveyor pallets move in the same manner as said chain. The drive system is located at one of the ends of the moving walkway whereas the elements responsible for tightening the system are normally located at the opposite end. The turnover of the conveyor pallets which travel the entire moving walkway in the lower part completing the return trip occurs at these end areas of the moving walkway.
The function of the tightening system is to assure minimum stress in the band/chain of pallets such that it works with tensile stresses through as much of its path as possible and to prevent the possible “pilling-up” of the chain in the operation due to low stress.
In the particular case of a flat walkway operating in the upwards direction (passengers enter through the end of the tightening system 2 and exit through the end of the drive unit 3) the stress distribution line 4 along the walkway as well as the zero tension level 1 of the moving walkway corresponds to that shown in FIG. 2, FTup being the climbing stress. In the turnover of the lower head the stress is mainly fixed by the action of the tightening system, from hereon, and in the forward direction of the walkway, the stress on the band/chain of pallets (FTup) rise due to friction forces generated as a result of the weight of the passengers applied on this branch together with the weight itself, until reaching its maximum value at the upper end of the unit right at the entrance to the drive unit 3. The stress is unloaded in the drive unit to a minimum value to then be increased along the lower return path as a result of the friction forces produced by the weight of the band of pallets itself until reaching the lower turnover where the stress is approximately that of the tightening system.
As can be deduced from this explanation, if the band of pallets lengthen, stress loss will occur in the band of pallets which will mainly appear in the lower return path for the upwards direction. As a result, applying a Tfup stress is necessary for assuring a correct operation of the system as seen.
FIG. 3 shows the diagram of stress distributions 4′ of a walkway in the downwards direction in which the zero tension level 1′ is shown. When the drive system pushes the band/chain of pallets the point of minimum stress will be at the exit of the drive unit 3. Depending on the loading state of the walkway, its length and the stress applied by the tightening system, this stress value can be negative as seen in FIG. 3. The stress increases little by little along the upper branch in the travelling direction until reaching the end of the tightening unit where the stress is basically that fixed by the tightening unit. Then the stress increases in the lower return branch as a result of the friction of the band of pallets along the travelling direction of the walkway until reaching the turnover of the upper end. The maximum stress value will be reached right at the entrance of the drive unit.
Therefore, it can be deduced that the stress which the tightening system must provide in this case will have to be greater than in the above case since the negative stress value must be prevented as much as possible at the exit of the operation.
If this stress is applied in a fixed and invariable manner to a bidirectional walkway in the upwards travelling direction, the band/chain of pallets and particularly its rollers will be subjected to stresses larger than that necessary in the turnovers which leads to unnecessary wear, therefore reducing its service life and the need to use more robust elements with a higher cost, since the upwards travelling direction will usually be the most common.
Kone's U.S. Pat. No. 7,861,843 B2 describes a tightening system varying its stress dynamically depending on the situation of the system or on the direction of rotation: The stress provided by the tightening system in the upwards direction will be less than in the downwards direction.